Add support for the Heroku-22 stack

* Adds binary generation and testing support for Heroku-22.
* Removes all EOL/deprecated runtime version build scripts.
* No longer set a fallback value for the `$STACK` env var, since it is always set on Heroku.

Runtime version support for Heroku-22 is as follows:
* Python 3.6 and older: Not supported since EOL.
* Python 3.7/3.8: Not supported since:
   - they are in the security-fix-only phase of their lifecycle
   - they reach EOL in 2023-06 and 2024-10 respectively, which is well
     before the EOL date of Heroku-22
   - upgrading from 3.7/3.9 to 3.9 is in most cases trivial, and
     so we should be encouraging users to upgrade.
* Python 3.9: Only the current latest patch release (3.9.12) supported
   (plus any future 3.9 releases).
* Python 3.10: All patch releases supported.
* PyPy: Not supported, since is deprecated, was only ever a beta
   feature, the PyPy versions available for Heroku-18/20 are
   significantly out of date, and usage is virtually non-existent.

GUS-W-10343718.

Author: edmorley

.circleci/config.yml

@@ -47,7 +47,7 @@ jobs:
     parameters:
       stack:
         type: enum
-        enum: ["heroku-18", "heroku-20"]
+        enum: ["heroku-18", "heroku-20", "heroku-22"]
     docker:
       - image: cimg/ruby:2.7
     working_directory: /mnt/ramdisk/project
@@ -87,4 +87,4 @@ workflows:
       - hatchet:
           matrix:
             parameters:
-              stack: ["heroku-18", "heroku-20"]
+              stack: ["heroku-18", "heroku-20", "heroku-22"]

CHANGELOG.md

@@ -1,8 +1,8 @@
 # These targets are not files
 .PHONY: lint lint-scripts lint-ruby compile builder-image buildenv deploy-runtimes publish
 
-STACK ?= heroku-20
-STACKS ?= heroku-18 heroku-20
+STACK ?= heroku-22
+STACKS ?= heroku-18 heroku-20 heroku-22
 PLATFORM := linux/amd64
 FIXTURE ?= spec/fixtures/python_version_unspecified
 ENV_FILE ?= builds/dockerenv.default

Makefile

@@ -58,10 +58,6 @@ PY27="python-2.7"
 PYPY27="pypy2.7"
 PYPY36="pypy3.6"
 
-# Which stack is used (for binary downloading), if none is provided (e.g. outside of Heroku)?
-# TODO: Remove this and require that STACK be set explicitly.
-DEFAULT_PYTHON_STACK="heroku-18"
-
 # Common Problem Warnings:
 # This section creates a temporary file in which to stick the output of `pip install`.
 # The `warnings` subscript then greps through this for common problems and guides
@@ -73,9 +69,6 @@ RECOMMENDED_PYTHON_VERSION=$DEFAULT_PYTHON_VERSION
 # This installs them into the path, so we can execute them directly.
 export PATH=$PATH:$ROOT_DIR/vendor/
 
-# Set environment variables if they weren't set by the platform.
-[ ! "$STACK" ] && STACK=$DEFAULT_PYTHON_STACK
-
 # Sanitize externally-provided environment variables:
 # The following environment variables are either problematic or simply unneccessary
 # for the buildpack to have knowledge of, so we unset them, to keep the environment
@@ -93,7 +86,7 @@ source "$BIN_DIR/warnings"
 
 if [[ -f "${ENV_DIR}/BUILD_WITH_GEO_LIBRARIES" ]]; then
   mcount "failure.unsupported.BUILD_WITH_GEO_LIBRARIES"
-  puts-warn "The Python buildpack's legacy BUILD_WITH_GEO_LIBRARIES functonality is"
+  puts-warn "The Python buildpack's legacy BUILD_WITH_GEO_LIBRARIES functionality is"
   puts-warn "no longer supported:"
   puts-warn "https://devcenter.heroku.com/changelog-items/1947"
   puts-warn

README.md

@@ -0,0 +1,20 @@
+FROM heroku/heroku:22-build
+
+ENV WORKSPACE_DIR="/app/builds" \
+    S3_BUCKET="heroku-buildpack-python" \
+    S3_PREFIX="heroku-22/" \
+    STACK="heroku-22"
+
+RUN apt-get update \
+    && DEBIAN_FRONTEND=noninteractive apt-get install --no-install-recommends -y \
+        libsqlite3-dev \
+        python3-pip \
+        python3-setuptools \
+    && rm -rf /var/lib/apt/lists/*
+
+WORKDIR /app
+
+COPY requirements.txt /app/
+RUN pip3 install --disable-pip-version-check --no-cache-dir -r /app/requirements.txt
+
+COPY . /app